Tracking and mitigation of quasiparticle poisoning errors in majorana quantum computing systems

Abstract

A computing system including a quantum computing device that includes Majorana islands at which Majorana zero modes (MZMs) are instantiated. The computing system further includes a controller configured to control the quantum computing device to perform a joint parity measurement at two or more MZMs. The controller is further configured to control the quantum computing device to perform quasiparticle poisoning (QPP) detection at the one or more Majorana islands to thereby generate error data. The error data includes one or more QPP indications associated with the one or more Majorana islands. The controller is further configured to receive the error data from the quantum computing device. The controller is further configured to update an accumulated error state of the one or more Majorana islands based at least in part on the error data, and to perform an update operation based at least in part on the accumulated error state.

1 . A method for use with a computing system that includes a quantum computing device, the method comprising:
 controlling the quantum computing device to perform a quantum computation including a plurality of logical computing timesteps that implement respective logical-level operations specified by a quantum code, wherein each of the logical computing timesteps includes:
 performing a plurality of physical computing timesteps at a plurality of physical qubits, wherein each of the physical computing timesteps includes:
 performing a plurality of joint parity measurements at a set of physical qubits included among the plurality of physical qubits; and 
 performing a plurality of quasiparticle poisoning (QPP) detections on the set of physical qubits to thereby obtain error data; and 
 
 subsequently to the plurality of physical computing timesteps, performing an update operation on the plurality of physical qubits based at least in part on respective results of the QPP detections included in the error data; and 
   outputting a quantum computation output obtained by performing the plurality of logical computing timesteps included in the quantum computation.   
     
     
         2 . The method of  claim 1 , further comprising, during each of the logical computing timesteps:
 controlling the quantum computing device to transmit the error data to the controller;   at the controller, compute update instructions based at least in part on the error data; and   controlling the quantum computing device to perform the update operation according to the update instructions.   
     
     
         3 . The method of  claim 2 , wherein:
 the update operation is a quantum error correction operation; and   the method further comprises computing the update instructions based at least in part on the quantum code.   
     
     
         4 . The method of  claim 3 , wherein the quantum error correction operation is performed subsequently to a physical computing timestep of the plurality of physical computing timesteps that is immediately prior to a non-Clifford logical operation. 
     
     
         5 . The method of  claim 3 , wherein the quantum error correction operation includes a Clifford logical operation that is performed subsequently to a non-Clifford logical operation. 
     
     
         6 . The method of  claim 2 , wherein the accumulated error state includes a Pauli operator sequence of two or more Pauli operators respectively associated with two or more of the joint parity measurements. 
     
     
         7 . The method of  claim 1 , further comprising controlling the quantum computing device to perform the QPP detections subsequently to each of the joint parity measurements included in the logical computing timestep. 
     
     
         8 . The method of  claim 1 , further comprising controlling the quantum computing device to perform two or more of the joint parity measurements in parallel. 
     
     
         9 . The method of  claim 1 , further comprising controlling the quantum computing device to perform two or more of the QPP detections in parallel. 
     
     
         10 . The method of  claim 1 , wherein:
 the quantum computing device includes a plurality of Majorana islands at which a plurality of Majorana zero modes (MZMs) are instantiated;   the joint parity measurements are performed at one or more of the Majorana islands; and   the error data indicates a change in one or more respective fermion parities of the one or more of the Majorana islands.   
     
     
         11 . A computing system comprising:
 a quantum computing device; and   a controller configured to:
 control the quantum computing device to perform a quantum computation including a plurality of logical computing timesteps that implement respective logical-level operations specified by a quantum code, wherein each of the logical computing timesteps includes:
 performing a plurality of physical computing timesteps at a plurality of physical qubits, wherein each of the physical computing timesteps includes:
 performing a plurality of joint parity measurements at a set of physical qubits included among the plurality of physical qubits; and 
 performing a plurality of quasiparticle poisoning (QPP) detections on the set of physical qubits to thereby obtain error data; and 
 
 subsequently to the plurality of physical computing timesteps, performing an update operation on the plurality of physical qubits based at least in part on respective results of the QPP detections included in the error data; and 
 
 output a quantum computation output obtained by performing the plurality of logical computing timesteps included in the quantum computation. 
   
     
     
         12 . The computing system of  claim 11 , wherein, during each of the logical computing timesteps, the controller is further configured to:
 control the quantum computing device to transmit the error data to the controller;   compute update instructions based at least in part on the error data; and   control the quantum computing device to perform the update operation according to the update instructions.   
     
     
         13 . The computing system of  claim 12 , wherein:
 the update operation is a quantum error correction operation; and   the controller is further configured to compute the update instructions based at least in part on the quantum code.   
     
     
         14 . The computing system of  claim 13 , wherein the quantum error correction operation is performed subsequently to a physical computing timestep of the plurality of physical computing timesteps that is immediately prior to a non-Clifford logical operation. 
     
     
         15 . The computing system of  claim 13 , wherein the quantum error correction operation includes a Clifford logical operation that is performed subsequently to a non-Clifford logical operation. 
     
     
         16 . The computing system of  claim 12 , wherein the accumulated error state includes a Pauli operator sequence of two or more Pauli operators respectively associated with two or more of the joint parity measurements. 
     
     
         17 . The computing system of  claim 11 , wherein the controller is configured to control the quantum computing device to perform the QPP detections subsequently to each of the joint parity measurements included in the logical computing timestep. 
     
     
         18 . The computing system of  claim 11 , wherein the controller is configured to control the quantum computing device to perform two or more of the joint parity measurements in parallel. 
     
     
         19 . The computing system of  claim 11 , wherein the controller is configured to control the quantum computing device to perform two or more of the QPP detections in parallel. 
     
     
         20 . A computing system comprising:
 a quantum computing device; and   a controller configured to:
 control the quantum computing device to perform a quantum computation including a plurality of logical computing timesteps that implement respective logical-level operations specified by a quantum code, wherein each of the logical computing timesteps includes:
 performing a plurality of physical computing timesteps at a plurality of physical qubits, wherein each of the physical computing timesteps includes:
 performing a plurality of joint parity measurements in parallel at respective sets of physical qubits included among the plurality of physical qubits; and 
 subsequently to performing the joint parity measurements, performing a plurality of quasiparticle poisoning (QPP) detections in parallel on the sets of physical qubits to thereby obtain error data; and 
 
 subsequently to the plurality of physical computing timesteps, performing a quantum error correction operation on the plurality of physical qubits based at least in part on respective results of the QPP detections included in the error data; and 
 
 output a quantum computation output obtained by performing the plurality of logical computing timesteps included in the quantum computation.